1. Field of the Invention
The present invention relates to an auger-type ice making machine and, more particularly, to a support structure of a lower bearing which is provided in a lower end section of an ice making barrel thereof.
2. Description of the Related Art
An auger-type ice making machine is a continuous ice making machine which is designed to rotate an auger in a vertical ice making barrel, scrape the ice which freezes and grows on the inner surface of the ice making barrel, and feed it out upwardly. A typical example of such auger-type ice making machine will be described with reference to FIG. 12. An auger 3 is supported, via bearings 5a and 5b, in a cylindrical ice making barrel 1 around which a refrigerant evaporating pipe 1a is wound. The upper bearing 5a is fixed onto the upper end section of the ice making barrel 1 via a pressing head 7, and the lower bearing 5b is fixed onto the lower end section of the ice making barrel 1 via a bearing housing 9. The bearing housing 9 is fixed with a flange onto a casing 11a of a drive unit which includes a drive motor 11. The auger 3 is linked to an output shaft of the drive motor 11 and is rotated to scrape the ice which freezes and grows on the inner surface of the ice making barrel 1 and feed it upwardly, thereby producing predetermined ice chips. The structure stated above has been used extensively as seen from the disclosure in Japanese Utility Model Laid-Open Nos. 62-45656 and 57-85169, Japanese Patent Laid-Open No. 58-21020, etc.
The conventional general structure described above is structurally advantageous in that the auger is axially centrally aligned with the output shaft of the drive unit to form a good shaft coupling free from eccentricity, since the bearing housing which supports the lower bearing of the auger is directly fixed onto the casing of the drive unit. This structure, however, is disadvantageous in achieving the best possible alignment or the like between the ice making barrel and the auger.
To be more specific, the first consideration is that the ice making barrel 1 with the evaporating pipe 1a wrapped therearound serves as a functional member which provides the inner peripheral surface thereof as an ice making surface and it also serves as a structural reinforcing member. As such structural member, it should have a thick wall to offer high rigidity and strength. On the other hand, however, the wall should be made as thin as possible to control the resistance of heat transfer to a minimum so as to improve the ice making capability. Hence, the ice making barrel is designed with a wall thickness that is a compromise attempting to satisfy the above two conflicting requirements at a practical level.
Secondly, in order to efficiently freeze and grow ice on the inner peripheral surface, i.e. the ice making surface, of the ice making barrel, it is required to set the distance (gap) between the spiral blade of the auger and the inner peripheral surface of the ice making barrel to an optimal value within a relatively small range. In addition, the wear on the bearings must also be taken into account. Failure to give careful consideration to these two points would cause the spiral blade to come too close to the inner surface of the ice making barrel, resulting in a shortened service life. The optimal gap based on such consideration ranges from 0.4 to 0.5 mm, for example, although it varies depending on conditions. As mentioned above, the structure wherein the ice making barrel is linked to the drive motor through the bearing housing is not entirely satisfactory because it incurs accumulated errors (manufacturing tolerance) of the constitient members. A possible solution to the problem of the accumulated manufacturing tolerances is to raise the grade of the manufacturing tolerances of the individual components included. This type of solution, however, unavoidably involves increased manufacturing cost in machining.
Further, as previously described, this type of ice making machine is designed to scrape a layer of ice, which has grown on the inner peripheral surface of the ice making barrel, and feed the scraped ice upwardly to compress and solidify the ice through the pressing head. This means that the ice making barrel is subjected to a heavy upward load. The load is transmitted to a bearing housing through bolts, which fix the bearing housing to the ice making barrel, and the load is transmitted further to the drive motor. At this time, the load is not always distributed evenly to a plurality of through bolts, causing the axial center of the ice making barrel to relatively tilt in relation to the axial center of the bearing housing and the axial center of the auger, thus changing the aforesaid gap. This prevents good ice making conditions from being obtained and it may also lead to a markedly shortened service life of the machine.